Question regarding shells and subshells when a script is run
I have the following script running with nohup on one of my servers:
All it's doing is watching a log file, and looking for errors (as indicated by E in the third column) and then checking to see if that error is a specific problem we're having, and if so, dumping some information about the interface. The script runs perfectly, and creates the dump files exactly as expected. The one thing I don't understand is why it seems to create two processes when it is run:
I assume it has something to do with creating subshells when the script is run, but as I (unfortunately) learned most of my scripting and whatnot from trial and error, and not from real book learning, simple things like this escape me.
I've tried to do some reading, and while I understand shells and subshells to a point in theory, I'm having a hard time understanding what's going on in practice. Could anyone give me the idiots explanation of why I'm spawning two processes to do one job? (I know the script isn't running twice at the same time...only one dump file is being created).
I have come across the topic of changing shells, does that mean that all Unix operating systems comes with a variety of shells built in and its up to the user to select a shell of his/her choice? (2 Replies)
Hi,
Would like to ask the experts if anyone knows how to run a script like this:
dtterm -title shell1
run process1 on shell1
dtterm -title shell2
run process2 on shell2
cheers!
p/s: sorry if i used the wrong forum, quite concussed after watching world cup for several nights; but I... (2 Replies)
Hi all,
I have a shell script which calls other shell scripts, depending on the input.
Within a.sh, I have a command which calls b.sh (ie. ksh b.sh)
Normally, we use the exit function to terminate a shell. However, if I choose to call exit from b.sh, I will return to the parent shell who... (4 Replies)
Hi,
Is it possible to use multiple shells in one script.
There are sometimes we need to club shell specific commands in single script.
for example in bash mode we use -e with echo to use Escape sequence but in ksh it is not required. How to tell a UNIX command to run in a specific shell.
... (2 Replies)
HI,
I would like to ask You about some good books or links where I can find information about shells, theoretical information.
I will be grateful if You can help me
And I have question about zsh loop
trivial script:
#!/bin/zsh
for i in {1..100000}
do
echo $i;
doneexec time is 10... (9 Replies)
All,
I am pretty new to Unix and still in the learning curve :) I have a simple requirement for which I did not get an answer yet (Atleast I do not know how to keyword the search for my requirement!!!).
I have an executable script my.script1 in a folder /data/misc/scripts/dev, which when... (5 Replies)
how to run an already developed script run against a list of ip addresses solaris 8 question.
the script goes away and check traffic information, for example
check_GE-VLANStats-P3 1.1.1.1
and returns the results ok.
how do I run this against an ip list? i.e a list of 30 ip addresses (26 Replies)
Hi
What is the command to run additional available shells on top of default shell. I am using bash
also how can i tell that the additional shells are actually running?
Also what is the advantage of running additional shells on top of your default login shell of bash?
Lastly... (1 Reply)
Hi, unix newbi here.
Im currently on the bash shell, what are the commands to run additional shells?
for example i want to run csh and then ksh?
Thanks.
BT. (2 Replies)
Hi to all,
i have the following problem...
i want to run three commands in a script in different shells... the first command is running always and is needed for the second on to run properly... example
# Procedure 1
xterm -e exec1 arg1 arg2
# Procedure 2
xterm -e exec2 arg1 arg2
#... (6 Replies)
Discussion started by: paladinaeon
6 Replies
LEARN ABOUT HPUX
nohup
nohup(1) General Commands Manual nohup(1)NAME
nohup - run a command immune to hangups
SYNOPSIS
command [arguments]
DESCRIPTION
executes command with hangups and quits ignored. If output is not redirected by the user, both standard output and standard error are sent
to If is not writable in the current directory, output is redirected to otherwise, fails. If a file is created, the file's permission bits
will be set to
If output from is redirected to a terminal, or is not redirected at all, the output is sent to
EXTERNAL INFLUENCES
Environment Variables
determines the language in which messages are displayed.
If is not specified in the environment or is set to the empty string, the value of is used as a default for each unspecified or empty vari-
able. If is not specified or is set to the empty string, a default of "C" (see lang(5)) is used instead of
If any internationalization variable contains an invalid setting, behaves as if all internationalization variables are set to "C". See
environ(5).
International Code Set Support
Single- and multi-byte character code sets are supported.
EXAMPLES
It is frequently desirable to apply to pipelines or lists of commands. This can be done only by placing pipelines and command lists in a
single file, called a shell script. To run the script using
features apply to the entire contents of file. If the shell script file is to be executed often, the need to type can be eliminated by
setting execute permission on file. The script can also be run in the background with interrupts ignored (see sh(1)):
file typically contains normal keyboard command sequences that one would want to continue running in case the terminal disconnects, such
as:
WARNINGS
Be careful to place punctuation properly. For example, in the command form:
applies only to command1. To correct the problem, use the command form:
Be careful of where standard error is redirected. The following command may put error messages on tape, making it unreadable:
whereas
puts the error messages into file
EXIT STATUS
The following exit values are returned:
The command specified by
command was found but could not be invoked
An error occurred in the nohup utility or the specified
command could not be found
Otherwise, the exit status of nohup will be that of the command specified.
SEE ALSO chmod(1), nice(1), sh(1), signal(5).
STANDARDS CONFORMANCE nohup(1)